1. Field of Invention
This invention relates to a method and device for solid phase microextraction and analysis and, in particular, relates to microextraction and analysis being carried out using various types of a single fiber or capillary which can be coated with various materials or uncoated.
2. Description of the Prior Art
Presently, in the organic analysis of environmental samples which involve the separation of components of interest from such matrices as soil, water, fly ash, tissue or other material, liquid extraction is traditionally used as the separation process. For example, water samples are usually extracted with organic solvent. Similarly, solid samples are leeched with an organic solvent in a SOXHLET apparatus. Methods based on solvent extraction are often time consuming, difficult to automate and are very expensive since they require high purity organic solvents and these organic solvents are expensive to dispose of. Further, the organic solvents usually have high toxicity and are difficult, to work with. In addition, the extraction processes can be highly non-selective. Therefore, sequential chromatographic techniques must sometimes be used to separate complex mixtures after extraction, significantly increasing the overall analysis time and the cost. EP-A1-159 230 discloses an extraction method of components in a liquid by placing packets of fibers in contact with said liquid in extracting the components.
Solid phase extraction is a known effective alternative to liquid-liquid extraction in the analysis aqueous samples. The primary advantage of-solid phase extraction is the reduced consumption of high purity solvents and the resulting reduction in laboratory costs and the costs of solvent disposal. Solid-phase extraction also reduces the time required to isolate the analyte of interest. However, solid phase extraction continues to use solvents and often suffers from high blank values. Further, there is considerable variation between the products offered by different manufacturers and lot-to-lot variation can be a problem when carrying out solid phase extraction procedures. Solid phase extraction cartridges available for manufacturers are normally constructed of plastic which can adsorb the analyte and increase interferences in the analysis. The disposable plastic cartridges used in the solid phase extraction process are first activated using organic solvent. The excess organic solvent is then removed and the sample to be tested is passed through the cartridge. The organic components from the sample. are adsorbed on the chemically modified silica surface of the material in the cartridge. Both molecules of interest as well as interferences are retained on the cartridge material. During desorption, a selective solvent is chosen to first remove the interferences. The analyte is then washed out of the cartridge. The analytical procedure from that point is identical to that used in liquid-liquid extraction. The analyte is first preconcentrated and the mixture is then injected into an appropriate high resolution chromatographic instrument. Steps involving the use of organic solvents are the most time consuming.